1. Field of the Invention
The present invention belongs to a technical field of recording a servo signal onto a magnetic tape and verifying the servo signal recorded on the magnetic tape. More specifically, the invention relates to a servo signal recording device capable of recording the servo signal at a given position on the magnetic tape with a high degree of precision, and a servo signal verifying device capable of detecting only an error in the position at which the servo signal is recorded, to perform the verification of the servo signal with a high degree of precision.
2. Description of the Related Art
In a field where a magnetic tape is used to record information, in order to perform appropriate record/reproduction of the information, a magnetic head which records/reproduces the information (hereinafter, also referred to as recording/reproducing head) must track a recording track on the magnetic tape accurately.
On the other hand, in recent years, there is a strong demand for an increase of storage capacity. In response to this demand, there is a tendency for the width of the information recording track to become narrower, whereby it becomes difficult for the recording/reproducing head to track the recording track accurately.
In order to deal with this problem, a servo signal is recorded on the magnetic tape, and when the information is recorded/reproduced, a magnetic tape device detects the servo signal by means of a servo signal reader (hereinafter, referred to as servo head). In response to the results from the detection, the recording/reproducing head is moved crosswise across the magnetic tape, to thereby ensure the precision of the tracking of the recording track by the recording/reproducing head.
Naturally, in order for the magnetic tape to exhibit a given level of quality, it is necessary that the servo signal be recorded with great accuracy into the prescribed position.
Recording of the servo signal is typically performed while the magnetic tape is transported, as is done in ordinary recording of magnetic information. Further, a magnetic head for recording the servo signal, or other such servo signal recording units, are in a fixed position with respect to the magnetic tape transporting system. However, factors such as the degree of precision of the transporting system and fluctuations in the shape of the tape (i.e., width, thickness) cause the transported magnetic tape to move (i.e., displacement attendant on transporting occurs) in the crosswise direction at the servo signal recording position, and this causes the servo signal recording position to fluctuate along the crosswise direction.
Known methods for circumventing those problems include a method of strengthening the regulation of the crosswise movement of the magnetic tape in the magnetic tape transporting system, or uniformization of the shape of the magnetic tape, and the like.
However, when the positional regulation for the transporting system is strengthened, a strong force is borne on the edge (side portion) of the magnetic tape, and there was a problem in that deformation, breakage and the like occur in the magnetic tape, which disadvantageously results in reduced productivity and yield.
Also, uniformization of the magnetic tape shape often requires improvement of a tape application device or a slitting device or the like. Thus, there was a problem of incurring a great burden in terms of cost, labor and the like.
Further, as described above, in the manufacturing process of the magnetic tape, the magnetic tape is transported along its lengthwise direction while recording the servo signal, as is done in typical information recording. However, it is not realistically possible to completely hold the magnetic tape in the prescribed position while transporting it. Thus, at the position of the magnetic head which records the servo signal, a movement (hereinafter referred to as displacement attendant on transporting) of the magnetic tape occurs along the crosswise direction of the magnetic tape which is being transported. As a result, an error is generated in which the recording position of the servo signal moves along the crosswise direction of the magnetic tape.
Therefore, during the manufacturing of the magnetic tape, in order to ship out a product of appropriate quality, the servo signal is verified after the servo signal is recorded.
The verification of the servo signal is typically performed using a verification device, which is exclusively used for this purpose, by reproducing the recorded servo signal.
For example, in the verification device, the servo signal is reproduced by a magnetic head used for the verification (a verification head), and from the reproduction results is obtained the position (i.e., the position crosswise along the width of the magnetic tape) on the reproduced servo signal as tracked by the verification head. Further, from this position is simulated a position to be tracked by the servo head of the magnetic tape device when the corresponding magnetic tape device records/reproduces the information on the magnetic tape. The difference between the result produced by this simulation and the position where the servo head should be tracking is calculated, and the quality of the servo signal is evaluated based on this difference, thereby verifying the servo signal.
However, there was a problem in that the servo signal tracking position, which is tracked by the verification head, varies due not only to an error in the servo signal position, but also due to a variety of factors attendant on the reproduction of the servo signal by the verification device.
The conventional servo signal verification is performed in a state where these factors are overlapping, and there was a problem that the servo signal recorded on the magnetic tape could not be verified appropriately.